In a spin MOSFET, the source and drain (S/D) electrodes are made of a magnetic material (a spin-polarized material) so that the transistor drive current can be varied depending on the relative magnetization configuration of the S/D electrodes. Spin MOSFETs are used in reconfigurable logics such as FPGAs (Field Programmable Gate Arrays).
In the S/D forming process for conventional CMOSs, a salicide (self-aligned silicide) process is normally used. In this process, a metal layer made of Co, Ni, or the like is formed after the formation of gate electrodes, and the metal layer is made to react with Si through a heat treatment, so as to form silicide. By this technique, the unreacted portions of the metal layer on the gate sidewalls are selectively dissolved in chemical solutions such as an acid, but the silicide is not dissolved in chemical solutions. Therefore, stack electrodes formed by stacking Si and silicide are formed in a self-aligning manner with respect to the Si surface of the foundation layer. Accordingly, MOSFETs can be formed, regardless of the alignment accuracy of lithography in the formation of contacts with Si. As the silicide, CoSi2, NiSi, or the like is used (see T. Ohguro, et al., “Ultra-shallow junction and silicide techniques for advanced CMOS devices,” Proceedings of the Sixth International Symp. On Ultralarge Scale Integration Science and Technology, the Electrochemical Society of Japan, pp. 275-295, 1997, for example).
Meanwhile, materials having high spin polarization of conduction electrons at room temperature are used for the electrodes of spin MOSFETs, and Co-based or Fe-based metal magnetic films are normally used. If Co, Fe, or CoFe alloy are silicided by using the same technique as that used in conventional MOSFETs, the resultant material is normally a nonmagnetic material, and the spin polarization becomes much lower. Even if high spin polarization is achieved by adjusting the composition of the silicide in a suitable manner, the composition becomes a metal-rich composition, and the resistance to acid cannot be achieved. That is, in the procedures for manufacturing spin MOSFETs, the process to form the S/D electrodes in a self-aligning manner through the same silicide reaction as those in conventional CMOSs cannot be used.
To practically use spin MOSFETs in LSIs, a self-alignment process is essential, but any reliable technique has not been proposed so far. Conventionally, there has been a well-known technique for forming the S/D shapes by photolithography and ion milling (see JP-A 2008-66596 (KOKAI), for example). By this technique, however, alignment with a FEOL (Front End of Line) is difficult, and accumulation of sophisticated technologies is necessary to avoid decreases in yield.
Miniaturization of spin MOSFETs is essential in fabricating large-scale production and obtaining higher performance. To achieve the miniaturization, there are demands for semiconductor devices that have magnetic S/D electrodes formed in a self-aligning manner, and methods of manufacturing the semiconductor devices.